Code Style. Dart
Use this page to configure formatting options for Dart files. When you change these settings, the Preview pane shows how this will affect your code.
In IntelliJ IDEA, Dart code is formatted using the dartfmt tool that has become an industry standard and is a part of the Dart SDK, see also the dart_style package documentation. The only configurable option is line length. By default, lines are 80 characters long. You can specify a custom value in the Line length field.
Learn more from Frequently Asked Questions about Dart Formatter.